The present invention relates to energy selective sample analysis systems and, more particularly, to an energy selecting slit assembly for use in such systems.
Energy filtered sample analysis systems commonly employ a source of charged particles and an imaging system to analyze the structure and/or composition of a sample under examination. The primary components of such systems include the charged particle source, suitable charged particle optics for directing a beam of particles towards and away from the sample under analysis, and a charged particle imaging system configured to provide an intelligible representation of the sample under analysis.
For example, and not by way of limitation, electron microscopes are capable of imaging individual atoms in a thin sample. However, the images produced by the microscope alone contain no direct information concerning the chemical composition of the sample, and the image quality degrades significantly if the sample is more than a few atomic planes thick. The chemical information can be provided by selectively imaging only with electrons that have experienced energy losses characteristic of particular atomic species while traversing the sample. Thus, electrons that have experienced non-representative energy losses are filtered out allowing further optics to create monochromatic images. These images can be combined to give maps of chemical or elemental distributions. They can also be used for a number of other analytical techniques. For example, and not by way of limitation, the images can be used to improve spatial resolution on thick samples and to remove inelastic signals prior to quantitative analysis.
A common method of energy filtering utilizes an energy-selected electron imaging filter in a transmission electron microscope. For example, and not by way of limitation, U.S. Pat. Nos. 4,851,670, 5,097,126, 5,640,012, 5,798,524, and 6,184,524, the disclosures of which are incorporated herein by reference, each relate to an energy filtered sample analysis system of this nature. The present invention is directed towards providing improvements in energy-selected electron imaging filters and other similarly configured charged particle filters.